Animal waste, animal byproducts and granulated chemical fertilizers can be added to garden soil to increase its nitrogen level, but other options are available, too. Household kitchen waste, for example, can be used as a homemade nitrogen fertilizer. Determine which material to use based on how much nitrogen it adds to soil as well as its cost and availability.
Fertilizers often contain nitrogen, phosphorous and potassium, or N, P and K, respectively. Their ratio is listed as three numbers on a fertilizer package, with each number representing the percentage of its element in the fertilizer. Fertilizer with a ratio that begins with a number followed by two zeros, such as 10-0-0, supplies only nitrogen.
Granular chemical fertilizer is available with a wide variety of nitrogen levels. Such a fertilizer's application rate varies with the percentage of nitrogen in the fertilizer. For example, the application rate for a 100-square foot-area is 1 pound of fertilizer that has a ratio, or analysis, of 10-0-0 or 1/2 pound of fertilizer with an analysis of 16-0-0.
Blood meal is dried waste from slaughterhouses. It has an analysis of 12-0-0. Apply 2 to 5 pounds of blood meal for every 100 square feet of garden soil that has a low amount of nitrogen, or use 1 pound of blood meal for every 100 square feet of soil that has a sufficient nitrogen level. Alternatively, apply 3 tablespoons of blood meal for every 10 square feet of soil, sprinkling it carefully by hand around plants after they have been planted. Do not apply blood meal within 3 inches of plant stems because it will burn them. It may make the soil more acidic.
Feather meal is made from byproducts of slaughtered poultry. It is 7 to 12 percent nitrogen. Add 2 1/2 to 5 pounds of it per 100 square feet of soil. Sprinkle 3 to 6 tablespoons of it per 10 square feet of soil around planted perennials. It takes more than four months for feather meal nitrogen to be released into soil. Apply feather meal to gardens in fall so the nitrogen will be available to plants in spring.
Bat guano has an analysis of 10-3-1 when it has been processed for nitrogen. It also adds microbes that help break down organic matter and improve soil. Spread 5 pounds of bat guano per 100 square feet of soil. Use it to add nitrogen around growing plants by mixing 3 teaspoons of it with 1 gallon of water and pouring the mixture over the soil.
Fish emulsion and fish meal are made from fish waste. Fish emulsion has an analysis of 5-2-2. It is water-soluble and used to add nitrogen to the soil of planted gardens. Mix 6 tablespoons of it per 1 gallon of water, and pour the solution over the soil around plants. Fish meal has an analysis of 4-2-2 to 9-7-0. It is spread over soil at the rate of 3 pounds for every 100 square feet.
Soybean meal provides nitrogen and small amounts of phosphorous and potassium. It has an analysis of 7-2-1. Apply 8 pounds of soybean meal for every 100 square feet of soil.
Coffee grounds and eggshells are sources of nitrogen and contain small amounts of phosphorus and potassium. The analysis of coffee grounds is 2-0.3-0.6 while the analysis of eggshells is 1.2-0.4-0.1. Apply 5 to 10 pounds of coffee grounds or 2 pounds of crushed eggshells for every 100 square feet. Coffee grounds may increase soil's acidity.
Grass clippings from mowing the lawn can be used to add nitrogen, phosphorous and potassium. The analysis of grass clippings is 0.5-0.2-0.5. The clippings offer the additional benefits of increasing the level of organic matter in the soil. They also create a more hospitable environment for worms as well as microorganisms that break down waste and improve the soil. Mow with a mulching lawn mower, and leave the clippings on the lawn to add these nutrients to the lawn's soil. Apply 50 pounds of grass clippings for every 100 square feet of garden soil that is low in nitrogen. Apply 30 pounds for every 100 square feet if the soil is not nitrogen-deficient.
The frequency and timing of nitrogen applications vary greatly with plant requirements and how quickly the soil drains. Plants in sandy soil may need more frequent applications than those in clay or loam soil. Also, some plants grow poorly when nitrogen is added to their soil while others are “heavy feeders” that require frequent applications. In general, nitrogen is added to garden soil in spring when plants begin to put on new growth or prior to planting. Nitrogen should be applied to lawns in late summer and fall.
Determine the amount of fertilizer that needs to be applied based on the application rate for the material used and the size of the area. Pour one-half of that amount into a drop or rotary spreader, and spread it over the area in one direction, such as while walking east and west. Pour the other one-half into the spreader, and spread it over the same area in the other direction, such as while walking north and south. Spread fertilizer around plants in gardens by hand. Wash the fertilizer off the foliage with water from a garden hose.
Rake the fertilizer into the top 1 to 2 inches of soil with a rake. Do not to rake too deeply or else you will injure shallow plant roots. Water the fertilized soil. Water helps wash the fertilizer down to roots.
Alternatively, after applying fertilizer to a garden that has not been planted, mix the fertilizer into the top 6 inches of soil by using a shovel or rototiller.